Effects of a gentling programme on the behaviour of laboratory rats towards humans

The present study investigated the effects of a gentling programme on the later behaviour of laboratory rats towards humans. For that purpose, 24 female Wistar rats were purchased from a laboratory animal breeding facility at the age of 21 days and allocated, genetically balanced, to an experimental and a control group. The animals were kept under standard laboratory conditions in groups of three. The experimental group was subjected to a gentling programme twice daily for 10 min per cage in the fourth and fifth week of life. This involved gentling and hand-feeding the animals. In addition, the animals were talked to during gentling. At the beginning of the 6th, 8th, 10th and 14th week of life as well as at the age of 6, 6.5 and 9 months the animals of both the experimental and the control group were subjected to tests in order to assess the rats’ behaviour towards humans. In the 14th week of life as well as at the age of 6 months the same test was additionally carried out by a person not familiar to the rats for the purpose of studying the animals’ behaviour towards unfamiliar persons.At each testing point a precisely defined, standardised test procedure was carried out, including among other things, repeated catching of the animals, neck grip, a hand test and a modified open field test involving a human stressor. Evaluation of the results was based on five primary endpoints which defined and summarised the most important parameters of the test procedure for the assessment of “tameness” towards humans.Significantly higher values in the primary endpoints were noted in the experimental group when compared to the control group in the test performed during the sixth week of life. The statistically estimated difference between the experimental and control groups was present until the age of 6 months. This suggested a higher level of “tameness” in the experimental group and a long-term effect of the gentling programme. Contrary to the experimental group, the control group showed a significant increase in tameness over time, which can be attributed to the animals getting used to the repeated tests or an age-related effect. The analysis of the difference between familiar and unfamiliar experimenters showed a borderline significant effect. The experimental and control groups were both slightly tamer with the unfamiliar person.The gentling programme had a beneficial long-term effect on the behaviour of the rats and proved suitable to reduce the laboratory rats’ fear of humans.